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cfq-iosched: fix possible problem with jiffies wraparound

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The RR service tree is indexed by a key that is relative to current jiffies.
This can cause problems on jiffies wraparound.

The patch fixes it using time_before comparison, and changing
the add_front path to use a relative number, too.

Signed-off-by: Corrado Zoccolo <czoccolo@gmail.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
This commit is contained in:
Corrado Zoccolo 2009-10-05 08:49:23 +02:00 committed by Jens Axboe
parent 30996f40bf
commit 48e025e63a
1 changed files with 6 additions and 3 deletions
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9
block/cfq-iosched.c
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@ -512,8 +512,11 @@ static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq,
rb_key = cfq_slice_offset(cfqd, cfqq) + jiffies;
rb_key += cfqq->slice_resid;
cfqq->slice_resid = 0;
} else
rb_key = 0;
} else {
rb_key = -HZ;
__cfqq = cfq_rb_first(&cfqd->service_tree);
rb_key += __cfqq ? __cfqq->rb_key : jiffies;
}
if (!RB_EMPTY_NODE(&cfqq->rb_node)) {
/*
@ -547,7 +550,7 @@ static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq,
n = &(*p)->rb_left;
else if (cfq_class_idle(cfqq) > cfq_class_idle(__cfqq))
n = &(*p)->rb_right;
else if (rb_key < __cfqq->rb_key)
else if (time_before(rb_key, __cfqq->rb_key))
n = &(*p)->rb_left;
else
n = &(*p)->rb_right;